This invention relates to a method of and apparatus for the testing of poles. Throughout the specification, the term xe2x80x9cpolesxe2x80x9d shall be used to include electricity, telephone and telegraphic poles; fence and retaining wall posts and the like.
This invention also relates to a pole support for ground poles and particularly relates to a pole support which can be driven into the ground next to a ground pole to support the pole against leaning or toppling over.
Power poles and telephone poles are conventionally formed from wood, steel or concrete and are pounded into the ground, or a hole is drilled into the ground and the pole is inserted into the hole.
Once the pole has been put into the ground, the upper part of the pole is arranged to receive power cables, data cables, telephone cables and the like. For some poles, the weight of these cables can be quite considerable and some poles contain additional devices such as power transformers which are quite heavy.
Occasionally, the poles need to be supported to an extent greater than that provided to the pole merely by being driven into the ground. It is known to provide additional support by driving a profiled steel member into the ground next to the pole and by bolting the pole to the profiled steel member.
As the pole can exert considerable force against the steel member, the steel member has required a complicated profile in order to prevent buckling under the force of the pole.
A disadvantage with these types of pole supports is that the required profile is complex and makes the supports expensive to manufacture. Also, existing profiles are not entirely satisfactory in their supporting ability.
Another reason for the complicated profile in existing pole supports is to reduce or eliminate sharp edges which can cause injury to
Pole supports are also required as a precaution when the strength of the pole is tested. One method for testing poles in the ground is to apply a load to the pole. A pole support is desirable to support the pole in case it breaks under test conditions.
Wood rot, bores, termites and other factors operate to reduce the strength, and therefore, the service life of poles. For safety reasons, the strength of the poles must be periodically checked and the future life of the poles established. As wood rot generally occurs below the ground level, a simple visual inspection is not sufficient and mechanical strength tests must be carried out.
To date, no simple, efficient and reliable test method has been available so poles are often replaced well before the end of their effective life. This naturally increases the operating expenses of the electricity authority.
It is an object to provide at least one simple method for testing poles.
It is a preferred object to provide an apparatus suitable for the method.
In one form, the invention resides in a method for testing a pole including the steps of:
calculating the minimum required strength of the pole and load to be applied to the pole equivalent to the minimum strength including any required safety factors,
applying a preset load to the pole equivalent to the calculated minimum strength, and
observing if the pole withstands the applied load without failure and so meets the minimum required strength.
In a second form, the invention resides in an apparatus for testing a pole including:
means to calculate the minimum required strength of the pole and load to be applied to the pole equivalent to the minimum strength,
means to apply a load to the pole,
means to measure the load applied to the pole, and (a) means to calculate the residual strength of the pole from the applied load, or (b) means to measure the displacement of the pole under the applied load,
means to calculate the residual strength of the pole from the applied load and the displacement, and
means to detect the pole failure.
In a third form, the invention resides in a method for testing the residual strength of a pole including the steps of:
applying a preset load to the pole,
measuring the displacement of the pole under the load, and
from the applied load and the displacement, calculating the residual strength of the pole from predetermined formula(e), tabulated scales, or by a programmed calculator or computer.
In a fourth form, the invention relates to a method for testing the residual strength of a pole including the steps of:
applying a load to the pole to cause the pole to undergo a preset displacement,
measuring the load applied to the pole, and
from the applied load and the displacement, calculating the residual strength of the pole from predetermined formula(e), tabulated scales, or by a programmed calculator or computer.
The minimum required strength of the tested pole and equivalent load to be applied to the pole may be calculated by a hand-held or desk top computer or predetermined from a formula(e) or table.
The load may be applied by pushing and/or pulling the pole at any height above the ground level and may be effected by a mechanical jack or turnbuckle, hydraulic or pneumatic ram, a winch or other suitable mechanical, hydraulic or electrical means which may be portable, mounted on wheels or vehicles.
The applied load is preferably measured by a load cell or other suitable equivalent means.
The applied loads and other test data as well as pole test results may be recorded manually or automatically by the use of any suitable computer system.
The displacement of the pole is preferably measured by displacement gauges, strain gauges or the like mounted on a reference frame.
The pole failure may be detected by a predetermined value of pressure drop on pressure gauges, noise level in acoustic devices, or by any other suitable means.
Stability of the pole in case of its failure can be provided by a safety frame or safety rope or pole buoy or safety clamps mounted to the boom of the crane of the pole testing vehicle or other heavy equipment.
The excessive movement of the pole is limited by a chain, rope, frame, pole buoy, bar, or clamps connected to the pole testing equipment or other heavy and stable machinery and objects such as concrete blocks, adjacent trees or the like.
The present invention is also directed to a pole support which may overcome the abovementioned disadvantages or provide the public With a useful or commercial choice.
In another form, the invention resides in a pole support for ground poles and which can be driven into the ground next to the pole, the support having a pair of spaced apart longitudinal end plates which are interconnected intermediate their ends by an intermediate plate, the end plates being spaced apart to allow the ground pole to pass at least partially between the end plates, each end plate having a front longitudinal edge which in use is adjacent the pole and a rear longitudinal edge which in use is directed away from the pole, the pole support having means to reduce sharp edge on the rear longitudinal edge.
In another form, the invention resides in a pole support for ground poles and which can be driven into the ground next to the pole, the support having a pair of spaced apart longitudinal end plates which are interconnected intermediate their ends by an intermediate plate, the end plates being spaced apart to allow the ground pole to pass at least partially between the end plates, each end plate having a front longitudinal edge which in use is adjacent the pole and a rear longitudinal edge which in use is directed away from the pole.
The pole support has a much simpler profile which still allows good support to the ground pole.
The pole support can be formed from steel plate or other material which is strong enough to be driven into the ground and to support the pole. The size, thickness and length of the pole support can vary depending on the forces exerted on the support, and the size and type of the pole.
The spaced apart longitudinal end plates are preferably substantially parallel to each other and are suitably sufficiently long to allow them to be driven into the ground to a suitable distance while still providing sufficient. length above the ground to provide support to the ground hole. This again can vary to suit, but lengths of 2 to 5 m are envisaged.
The width of the longitudinal end plates can vary depending on the degree of support required and the size of the pole. For instance, increasing the width of the end plates will increase the stiffness of the pole support and therefore the ability of the support to withstand forces applied to it. Increasing the thickness of the end plates will also achieve a similar result.
For manufacturing and transportation reasons, the end plates should not be excessively wide, but the plates should have sufficient width to allow the support to be hammered into the ground using the upper edge of the end plates (and possibly the intermediate plate) as a hammering surface.
The spacing between the end plates will vary depending on the diameter or cross-sectional size of the pole. As most power poles are between to 50 cm in diameter, it is preferred that the end plates are similarly spaced apart such that the ground pole can pass at least partially between the end plates. For reasons of safety, it is preferred that there is minimal gap between the end plate and the outer surface of the pole which could snag fingers of passers by or become a collection point for dirt and debris which may reduce the effective life of the pole.
The spacing between the end plates can be determined by the width of the intermediate plate. It is preferred that the end plates and the intermediate plates are all formed from the same material which is suitably steel, and that the plates are integrally formed together, or welded together to form a strong rigid structural unit which can be driven into the ground without falling apart. The intermediate plate preferably extends entirely along the length of the pole support by which is meant that the intermediate plates and the end plates are all of the same length.
Each end plate and the intermediate plate is preferably substantially rectangular when viewed in plan. Each end plate has a front longitudinal edge and an opposed rear longitudinal edge. The front longitudinal edge is defined as the edge which extends towards the pole, while the rear longitudinal edge is the other edge.
For reasons of strength and improved use, it is preferred that the end plates are plate-like which present longitudinal edges which are approximately at right angles and therefore present a quite sharp hard steel edge which can cause injury.
For this reason, another form of the invention includes a means by which the sharp edge can be eliminated or at least reduced to provide a pole support having suitable safety characteristics.
In one form, this can be achieved by providing a curved portion on or adjacent the rear longitudinal edge of each end plate. The curved portion can be formed by bending the longitudinal edge inwardly. Alternatively, a separate curved portion can be attached by suitable means to the rear longitudinal edge, for instance by spot, welding. In a further alternative, the means can include a rod or tube which is attached by any suitable means to the rear longitudinal edge to eliminate or at least partially reduce the sharp edge. In a further alternative, a cover plate or cover member can be positioned over one or both of the rear longitudinal edges to remove the sharp edge.